Weft-straightening apparatus and method



Sept 1, 1964 F. w. HOFFMAN WEFT-STRAIGHTENING APPARATUS AND METHOD Filed sept. 12. leso 4 Sheets-Sheet 1 Q Lawa@ GG va o@ QQ I4 JNVENTOR. FREDERICK W. HOF FMAN sept. 1, 1964 F. w. HOFFMAN 3,146,511

WEFT-STRAIGHTENING APPARATUS AND METHOD Filed Sept. l2, 1960 4 Sheets-Sheet 2 FREDERlCK HOFFMAN Sept. l, 1964 F. w. HOFFMAN 3,146 511 wEFTsTRAIGHTEN1NG APPARATUS AND METHOD Filed Sept. l2, 1960 4 Sheets-Sheet 3 8O A E55 s 35 o o@ M l O@ *I I mgl 1 Y OQO :HAMM/L 0"@ JEYWEFLW O O 26 l O O gm r E E l INVENToR. FREDERICK VV. HOFFMAN m 2 i q'r-roma Sept. l, 1964 F. w. HOFFMAN WEFT-STRAIGHTENING APPARATUS AND METHOD Filed sept. 12. 1960 4 Sheets-Sheet 4 ow vx N m: WN .Aww AH m m MM T N K T EC F au V F mv WR O EL @H n mmh R El H Ov V Nm. Y m mm B m- 1% v FN mn A mm 24E@ N959 SNN NN mm 1 Nm VM n m 2 mm mm 4|! om w w w /wfwm w.. 21 -m.. n wwN.. @WJ o m n W2@ F m3 .Q v N m.

United States Patent O 3,146,511 WEFT-STRAlGHTENlNG APPARATUS AND METHOD Frederick W. Hoffman, 318 Lafayette St., Pawtucket, RJ. Filed Sept. 12, 1960, Ser. No. 55,294 9 Ciaims. (Ci. 25--51.4)

This invention relates to improvements in apparatus for straightening skewed woven material. More particularly, the invention is directed to a novel method and means in association with a tentering machine for continuously correcting skew in a traveling web of cloth or textile fabric and for maintaining the desired right-angular relation between the warp and weft threads thereof as the moving web or fabric is guided along a predetermined path through such tentering machine in the course of finishing operations subsequently performed on such web or fabric leaving the tenter following straightening.

It is well known in the textile finishing art that woven textile material, such for example, as a web of cloth or woven fabric, often enters the tentering machine with the weft threads disposed widthwise of such fabric in a skewed off-perpendicular condition to the longitudinal warp threads thereof. Furthermore, this condition of skewed weft threads frequently may occur in a traveling woven fabric or cloth web in its passage from the tentering machine to the usual drying cylinder of standard drier equipment or to other well known items of finishing room equipment. Also, straightening of the weft threads is usually needed after putting the woven cloth web or fabric through customary bleaching, dyeing or printing processes. This skewed condition mentioned above of the woven textile material whether leading or lagging is objectionable and must be eliminated if faulty goods are to be prevented.

To avoid excessive skewing conditions some tentering machines in the past have been equipped with manually controlled means by which the woven material when it was observed to be skewed could be straightened by intervention of the machine operator. Such manually operable means, however, were found to be dependent upon the alertness and skill of the tenter hand and because of the various human factors involved did not prove too satisfactory.

In another instance, an electro-mechanical system including tandem pairs of pivoted detecting rollers has been proposed having the rollers disposed in the vicinity of the selvage edges of the textile sheet and actuated by the lateral stretching of the latter and also by the presence of modified distortion of roller engaged portions of the warp threads thereof due to skew or bow of the weft threads of the stretched sheet, this type of arrangement being disclosed in U.S. Patent No. 2,795,029. However, where such rollers are used there is a tendency that the rollers will either leave a mark on the cloth or that their contact with the cloth will flatten down the cloth surface thus engaged.

Also, apparatus utilizing photoelectric cell equipment have been employed in this art as disclosed, for example, in U.S. Patents Nos. 2,106,611 and 2,106,612 for detecting and automatically controlling skew and effecting straightening of the weft in woven textile material. However, many of the known photoelectric arrangements while performing satisfactorily are not accepted as being an ideal solution for this problem as they require the use icc of additional structural parts and equipment which necessitate a substantial reconstruction of standard tentering machine structure for their application thereto as well as the further attendant expenses for such changes together with the increased costs incurred thereby in the subsequent finishing processes performed on the unskewed tentered fabric or web.

lt is, therefore, the primary object of the present invention to eliminate the foregoing prior art apparatus along with their attendant diiculties and to accomplish weft detection and proper straightening control of woven textile material in an eiiicient and improved way by use of different and novel apparatus and a new method of using the same.

Another object of the invention is the utilization of any marked variations in pressure transmitted to the chain rails from the longitudinal side edges of the moving cloth being tentered and due to the deviations from uniform tension of the woven textile material across its width as an indication of the magnitude and direction of skew present in the woven textile material at the delivery end of the tenter for correcting such skew condition automatically.

A further object of the invention is to provide novel apparatus employing electro-mechanical force-responsive means variable in accordance with the magnitude of the instantaneous conditions of compressive force or pressure transmitted from the side edges of the traveling sheet to directly actuate such means for electrically energizing the same and the utilization of the thus-derived electrical output for controlling the skew of the sheet and rendering it uniform.

A still further object of the invention is to provide a novel apparatus of the described class which is so constructed that it is actuated by and makes use of the variations in pressure laterally applied by the selvage edges of the moving sheet with respect to the longitudinal guiding members therefor to activate and generate electrical indications which operatively control mechanism so as to appropriately speed up or slow down the lagging or the leading edges respectively of the sheet and thus correct any faulty skew condition previously present in the tentered sheet.

Another object of the invention is to provide an improved and efficient weft-straightening apparatus of this class which will be simple to apply to existing standard tentering machines, which will be economical to manufacture and easy to maintain, and which will be reliable in operation as well as being one which will be sensitive and automatically responsive to the presence of a very small amount of skew existent in the tentered woven textile material.

According to the present invention, I have found that automatic and continuous detection of skew of the weft threads in woven textile material in a tentering machine and the desirable weft-straightening treatment of the same as it moves therethrough to properly correct this skewed condition and result in delivery of the traveling cloth web or fabric therefrom at the proper speed for processing in subsequent mill-finishing equipment, can be accomplished and controlled in response to variations in electrical control indications which are set up by and in direct proportion to the magnitude and duration of the variations in pressure in two opposed groups of fabric-holding chain clips and exerted thereby against their guide rails sure will be detected by the strain gauges.

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in the tentering machine, preferably at the delivery end portion thereof, as the cloth web or fabric sheet moves therethrough whereby straightening of the latter is restored and maintained.

In accordance with the present invention, I further contemplate an improved method and means of continuous detection of skew in tentered cloth by providing oppositely located portions of the usual chain sides of a conventional tentering machine at the delivery end thereof with a series of load cells or strain gauges, the latter being of the type incorporating an electrical resistance bridge internally of each unit. These load cells or strain gauges in the arrangement contemplated herein utilize the pull of the usual clips against the vertical sides or edges of the chain rails at such end portion of the tenter so as to generate an electrical output the indications of which are connected to operatively energize an electrical network including a Wheatstone bridge circuit and a pair of bridge rectifers. Thus, in accordance with this invention, the output would be an electrical signal giving an indication of lboth amount and direction of skew as the cloth leaves the tentering machine.

Hence, on straight cloth when no skew occurs, the pressure on the last few clips on the inside flange of the chain rail on one side is equal and should be the same as that applied to the inside flange of the other side by the clips associated therewith because of the tension of the tentered cloth. Consequently, there would be no difference in the indications from the load cells or strain gauges on one rail as compared to the indications from the load cells or strain gauges simultaneously energized on the other and opposite chain rail member.

If, however, the cloth leaving the tentering machine is skewed, that is, one edge or selvage of the cloth is displaced either forwardly or rearwardly with respect to the other edge, an electrical signal is produced that gives an indication of both the amount and direction of skew as the cloth leaves the tentering machine. The electrical signal is produced by arranging strain gauges on both sides of the moving cloth and measuring the compressive forces of the edges. Thus, if the compressive pressure of the last few clips engaging one cloth edge on a flange formed on one side of the rail over which the cloth moves is less than that of the corresponding clips engaging the opposite edge of the cloth, a difference in pres- This will be particularly apparent when the moving cloth is skewed since one end of the weft threads will have passed from engagement with the associated chain, while the other yend of these weft threads across the cloth width will still be held by the corresponding clips of the chain associated therewith. Consequently, the resulting electrical output indications transmitted to the network system and received from the load cells or strain gauges on the side of the chain rail supporting the ahead selvage will be much less than those transmitted by the load cells or strain gauges "carried on the opposite side engaging the lagging selvage.

As a result, these electrical output indications derived as abovestated are received simultaneously into the network system where they produce electrical output signals which function to control either a differential motor or an amplidyne in a manner effective to regulate the chain-operating devices to slow down the chain on the leading edge of the tentered cloth and at the same time to cause a speed up of the chain of the lagging cloth edge whenever the moving cloth approaches the vicinity and also arrives at the load cells or strain gauges in a skewed condition.

Other objects, features, and advantages of this invention will become apparent from the following description when read in conjunction with the accompanying drawings and the novel features will be particularly pointed out in the appended claims In the drawings:

FIG. 1 is a schematic plan view of a tentering frame arrangement embodying one form of the present invention;

FIG. 2 is a fragmentary plan view on enlarged scale of the chain driving end portion depicted within the dotted rectangular outline of the FIG. 1 tenter arrangement and showing one group of the load cells applied thereto;

FIG. 3 is a vertical section on enlarged scale taken substantially on the line 3--3 of FIG. 1;

FIG. 4 is a schematic plan view of another arrangement of a tentering machine embodying the invention wherein the tenter is disposed in conjunction with a known type of straightener preceding the tenter;

FIG. 5 is a schematic plan view of a third arrangement showing the invention applied to a tentering frame which is utilized in conjunction with a following straightener;

FIG. 6 is a detail plan view of a fragmental portion of straight woven material (without skew) when properly traveling longitudinally through and acted upon in a tentering frame to which my invention is applied;

FlG. 7 is a detail plan view of a fragmental portion of woven material with skew which requires automatic correction of the latter as it passes longitudinally through a tentering frame equipped according to my invention;

FIG. 8 shows a suitable schematic electrical control circuit diagram in association with the apparatus of the present invention;

FIG. 9 is a fragmentary partial cross-sectional view on enlarged scale of the left half portion of the vertical sectional view illustrated in FIG. 3;

FIG. 10 is a schematic representation in electrical circuit diagram form of a miniature strain gauge bridge within one of the force transducers used in the system of my invention;

FIG. 11 is a pictorial end view of the transducer representation depicted in FIGS. 9 and 10 looking at the base or prong end thereof;

FIG. 12 is an enlarged fragmentary cross-sectional View of the upper chain rail Wall portion housing one of the yieldable plunger plates as seen in FIG. 9; and

FIG. 13 is a rear end view of one of the plunger plates showing its triangular spring mounting arrangement.

Referring first to FIG. l, there is represented at 10 a length of woven textile material such, for example, as a sheet of cloth or fabric which travels longitudinally through the tentering machine or frame from the entering end thereof in the direction of the arrow. The numerals 12 and 13 designate the usual clip-carrying movable tenter chains which are employed in connection with the woven cloth web or fabric sheet 1t) to drive and stretch the same laterally as it comes from the loom. The tentering machine, or tenter as the trade refers to it, is represented herein as comprising the two endless chains 12 and 13 abovementioned, each of which passes over the respective end drums or wheels 14, 14 and 15, 15', the latter members being suitably driven by an electric motor 16 through the cross-shafts 17 and 17 connected by appropriate gearing indicated at 1S, 19, 20' and 21 respectively and shafts 22 and 23 to produce the proper speed of the chains.

The cross-shafts 17 and 17' have inserted between them a differential gearing connection device 24, driven by the motor 16, the purpose of which will be described later.

Inasmuch as the main purpose of the tenter is to stretch the traveling woven material laterally, the longitudinal cloth driving runs of the two chains 12 and 13 are arranged to be slightly divergent to each other from the entering to the delivery end of the tenter in the well known manner of such machines as they are guided in and travel along their respective longitudinal chain rail members 25 and 26. To this end, each of the chain rail members 2.5 and 26 is provided with an upstanding T-shaped head portion 27 having undercut open outwardly-facing slots 27a and 27h extending longitudinally along its opposite sides underneath its T-head for receiving and guiding the rearwardly projecting tongue extensions 85 of each of a series of the usual cloth-engaging tentering clips 28 which are attached to and carried by the tenter chains 12 and 13. Also, the linear runs of such chains which extend between the particular pair of associated drums or Wheels 14, 15 and 14', 15, respectively, are suitably supported in and slide along the respective longitudinal grooves 2721 and 2'7b which are open in the top of each of the guide rail members and 26, see FIGS. 2, 3 and 9. These guide rail members are of like construction so that the description of one will suflice for the other.

The cloth-engaging tentering clips 28 which are mounted on the chains 12 and 155 may be of any of the well-known clip types used in the art but, as hereshown, they are of the type which carries the usual pivotally mounted dog 29 (see FIG. 9) having the upwardly projected tail 3i). Each dog 29 normally is pivotally fulcrumed as at 31 so that the action of gravity will cause its tip 32 to move to a position on the clip 23 for firmly clamping the woven material 1h against the adjacent lower plate portion 33 thereof which carries thereunder the usual roller chain element 34.

Drums 14, 1li and 15, 15' are of conventional structure and include top located disk or wheel portions 35, 35 and 3:5, 36 respectively which are of proper diameter and positioned to engage the tails 30 of the arriving clips 23 to move the dogs 29 thereof to their release position against the pressure effected by gravity. Thus, as each clip 28 leaves the drum 1d or 14 the particular dog 29 pivoted on such adjacent clip clampingly engages the selvage edge region of the woven textile material occupying the so-ealled bite of the clip and as each clip 2.8 of the chains reaches the respective disk or wheel portion 36, 36 of the drums 15, 15', the particular dog 29 thereof is rmly pushed in a direction to release the woven material that previously was held thereby when it reaches the delivery end of the tenter. Although not shown in FIGS. 1 3, the apparatus embodied therein will normally include straightener rolls that will be located before the drums 1d, 14' and will further include a movable straightener member associated with the straightener rolls. Such a construction is shown in FIG. 4 wherein the straightener rolls are indicated at 78, 79 and a swinging straightener member associated therewith is indicated at S.

The foregoing described structure is well known conventional tentering machine construction and no claims are made therefore in the present invention.

As contemplated by the present invention, the tentering machine arrangements herein illustrated each are providede with my novel weft-detecting, straightening and controlling means which is arranged proximate to or at the delivery end portion of the machine. The force-responsive members of my invention may be part of tandem chain rail conversion members to replace the usual sections of a standard tentering frame, or they may be incorporated in the rail members when the tenter is built.

As illustrated in FiGS. 2, 3, 9 and l2 of the drawings, but purposely omitted from the schematic representations of FIGS. l, 4 and 5 thereof in the interest of clarity of illustration of the latter views, the guide rail member 26 therein shown includes in its structure a vertical longitudinal wall element 4t? which forms the inner upright side wall member of the open chain-guiding groove Z7a disposed adjacent one the selvage edges of the cloth to be tentered and customarily occupied by the inner run of the cloth-advancing chain 13 of such chain rail. Disposed at or close to the delivery end portion of the tentering machine are a plurality of electrical resistance-type forceresponsive devices 42 which are operatively arranged, both mechanically and electrically, in accordance with this invention. Preferably the devices 42 are positioned 6, at opposite side edges of the advancing cloth sheet 10, and near to the delivery end portion of the machine of such sheet therefrom, one or more of these force-responsive devices 42 being mounted for actuation by the sidewise pressure or force existent at the contiguous selvage edge of the moving tentered cloth sheet as it is advanced and arrives at, forcibly engages, and moves past these respective devices. To this end, the wall elements 40 of the guide rails 25 and 26 at or in the vicinity of the cloth delivery end portions of the tentering machine are each equipped with an electrical type strain gauge or load cell generally designated 42 which is detachably aixed in a horizontal position to a longitudinal extending arm 43 of a strip-like mounting bracket 44 of generally U- shape that is firmly held in position, as by bolts 45, in an upright inverted position to the adjacent flanged wall portion 40 of the particular rail member 25 and 26.

Various types of electro-mechanical strain sensitive gauges or load cells 42 commercially available on the market may be employed for converting the force output of the chain clips 28 into electrical control indications. For example, the electrical output of a force transducer of the desired range, as manufactured by Dynamic Instrument Co., Inc., Cambridge, Massachusetts, is found practicable and is the type which I utilize in the illustrated embodiments of the invention herein disclosed.

This force transducer 42 is a resistance type device in which the electrical output of the transducer is derived from a miniature unbonded strain gauge in the configuration of a four-arm resistive Wheatstone bridge 5t) (see FIGS. 8 and l0), the unbalance of the latter being effected by the axial reeiprocatory movements of a precision sensing probe 51 in linear response to the amount of lateral pressure or force variations with which the respective chains 12 and 13 individually and directly bear against a yieldable plunger plate 52 adjacent the particular chain, one or more being mounted in each of the rail walls 4t?, and which, in turn, are transmitted through said plunger plates 52 to actuate the respective probes 51 to produce a resultant change in the length of each unit length of at least one of the resistance wire arms of this miniature Wheatstone bridge Si? with a resultant proportional change in the electrical resistance of each unit length of said wire, by reason of the principle known as hoissons law.

Each of the yieldable plunger plates 52 which may be either circular or rectangular in shape is disposed for reciprocating movement within a recess 53 of corresponding shape formed in the chain-facing surface 54 of each of the rail walls 49 so that it may be depressed flush with the surface of the wall from the position shown in broken outline in FIG. l2 when engaged by and subjected to the compressive force exerted by the clips 23 through the particular chain 12 or 13, as the latter slides over the plates S2. In the form here shown, see FIG. 13, the yieldable mounting of the plate 52 is achieved by means of a triangular arrangement of coil compression springs 55 which are housed in suitable bores 56 and respectively encircle suitable guide pins 57 projecting from and affixed to the back face of the plate 52.

Also projecting from the center of the back face of the plate 52 is a plunger element 53 which reciprocates in a suitable bore 59 in the chain rail wall 4t), the plunger element 53 being of such length that the enlarged circular head 6@ at its outer end will terminate outside the wall it? when the plate is at rest in its dotted position and will bear against the actuating probe 51 of the forcetransducer 42.

rthe head 64) reciprocates with the plunger element 58 in the circular bore 61 formed in the outer face of the rail wall 4t) and has sutiicient movement to act as a detent for limiting the movement of the plate 52 to its dotted position when the head is drawn against the bottom of the bore 61 by the action of the springs 55.

In FIGS. l() and 1l I have shown a schematic electrical diagram of such a force transducer 42 just described. As

there illustrated the legend designated in this figure is as follows:

A=Excitation B=Output signal DzExcitation E=Output signal H :Ground connection If desired, however, the force transducer structure just described whichV I employ may be replaced by a plurality of Emery load cells of the proper force range capable of delivering electrical output indications corresponding to the existent pressure variations at the selvage edges of the sheet and effective to operate the connected speed control system which. regulates the chain movements. These Emery load cells are known devices in the engineering field and are produced by The A. H. Emery Company, New Canaan, Connecticut.

With the above-described apparatus, it will be seen that if the weft condition of the woven textile material l@ passing through the tenter is straight, that is, without skew as depicted in FIG. 6, there will be even and equal pressure or compressive force exerted laterally by the cloth edges via their clamping clips 2S of both chains i2 and I3 against vertical surfaces of the respective outer chaingroove forming wall members of the longitudinal chain rails 25 and 26, respectively. The side arrows of the force diagram at the sides of FIG, 6 represent this equal pressure condition.

If, however, the traveling woven textile material or cloth web l@ should be in a skewed condition as it approaches and/or arrives in the neighborhood or at the delivery portion of the tentering machine, such condition, for example, being depicted in FIG. 7, then unequal compressive force or pressure will be exerted by these particular tenter clips 2S of the chains i2 and i3 laterally against the respective rail side walls above-mentioned of their chain rails. Thus, the force diagram shown at the sides of FIG. 7 represents with its lines of arrows this unequal pressure condition.

Hence, these oppositely disposed groups of tenter clips 28 will exert unequal pressure or compressive force on the movable probes l of the respective strain gauge type force transducers or load cells to actuate them and, in turn, will excite the same thereby producing corresponding variations of electrical energy flowing through the miniature resistance type strain gauge bridge thereof so as to generate electrical output signals proportional thereto.

These skew error electrical output indications thusderived are fed into the input of the control amplifier CA of an amplidyne drive system to the usual chain-operating mechanism of the tentering machine such as represented in the electrical circuit diagram illustrated in FIG. 8.

The amplidyne generator AG in such a system functions as an electro-mechanical power amplifier in which amplitied power output is very great in comparison to a small power input, and is a known device to those skilled in the art. In FIG. 8 the amplidyne AG is symbolically depicted as a conventional D.C. generator to which there has been added a second set of electrical brushes 65 connected by a curved shorting bar 66. An A.C. motor 67 is directly connected to the amplidyne generator AG to drive the same. The polarity and voltage variations of the output signal from the control amplifier CA in response to the applied signal thereto control the amplidyne generator AG and consequently its electrical output to the differential motor DM.

The electrical output signals of the control amplifier iCA after being amplified by the circuits thereof and varying in response to the force variations proportional to the skew conditions are fed to the tenter differential motor DM so as to control its speed and, in turn, that of the differential device 24- thereby controlling the speed of the operating mechanism of the chains 12 and t3 to appropriately increase the speed of one chain while simultaneously decreasing that of the other appropriately and for sufficient time to effect the necessary straightening of this skewed condition and attain uniform speeds of both chains l2 and 13.

Reference now is made to the control circuit diagram of FIG. 8, wherein the above-mentioned change in current flow of the electrical energy and voltage signals input thereto received from the force trandsucers or load cells 42 is made use of to give a response to the applied compressive force or presence of a concl'tion of skew and to effect a straightening of the material to remove the skew. Although, as previously stated, various forms of load cells or strain gauges may be employed to effect these results in response to a change in electrical energy, i.e. elecltrical current, of the output of one or both of the force transducers or load cells, I now shall describe a preferred form of apparatus and system which I employ in practicing my invention.

It is to be understood, however, that the schematic circuit diagram shown in FIG. 8 is for the purposes of illustration only of an embodiment of the invention for depicting its nature and principles of operation.

The FIG. 8 electrical circuit diagram here shown is not intended to restrict the invention but instead is representa- :tive of one of various electrical control drive systems incorporating a control amplifier and the various energizing electrical and electronic circuits which can be employed with electrical strain gauges or load cells in accordance with the present invention and which will give satisfactory and effective performance in the successful practice of my invention.

The apparatus of FIG. 8 in its entirety comprises a control amplier CA with its amplifying electrical circuits; the transformer power supplies and associated rectiers; an amplidyne generator AG; and a differential motor DM electrically controlled by the latter and drivingly connected to the differential device 24.

The operation of the apparatus is as follows:

Assuming the condition that there is no signal at Dl-Dg set (balance) the potentiometer 70 so that the same voltage is obtained at points 71 and 72. When this happens these voltages will then act on the grids of the two 6V6s so that the same voltage is obtained at the two amplidyne fields 73 and 74. This means that the field 73 is exactly balancing out the eld 74 because the two fields thus set act against each other. Therefore, because they are balancing out there is no output voltage from the armature of the amplidyne AG. Hence, there is no voltage input into the D.C. differential motor DM. Then if a signal is present at D1-D2 so as to make D2 less than the voltage signal into D1 then there is present more voltage at D1 than at D2. Consequently there is more voltage at the grid of the coil 73 and less voltage at the plate 75 of that particular 6V6. Therefore, the coil eld 74 overbalances the field 73 and begins to get voltage from the armature of the amplidyne AG so that the D.-C. differential motor DM begins to rotate in the desired direction. The D.-C. motor DM is stationary when there is no input voltage to it, i.e., no output voltage from the armature of the amplidyne AG.

When the signal applied at D2-D1 is such that D2 is more than D1, the converse occurs and the D.-C. differential motor DM rotates in the opposite direction by reason of the voltage from the amplidyne armature AG. By reason of the voltage amplification of the 6SL7 added to that of the amplidyne AG, a great amount of power amplification is thus effected.

One or the other limit switches LS-l or LS-Z opens when the usual swinging straightener such as indicated at S in FIG. 4 and driven by the D.-C. drive motor 80 reaches its extreme limit of tilting of the usual straightener rolls associated therewith in either direction, this opening of the particular limit switch LS-l or LS-Z depending on which side of the double tube 6SL7 is acting.

When the tilting straightener rolls of the type indicated at 78 and 79 in FIG. 4 come over and Contact the limit switch LS-l or LS-Z disposed at that location, the normally open Contact members of such switch (not shown) close, and the normally closed contact members (not shown) open. When these normally closed contacts open the particular amplidyne field 73 or 74, as the case may be, is disconnected from its associated 6V6 tube. At the same time the foregoing takes place the normally open contact members are closed and this consequently applies voltage to the usual cathodes of the two electronic tubes designated 6V6 preventing the still connected amplidyne field from operating the differential motor DM in the reverse direction, but allowing this motor to operate when the overskew situation has ended. In other words, opening of the limit switches LS-l and LS-2 partially shorts out the two 6V6 electronic tubes by voltage on their cathodes resulting in deadening the action of the amplidyne so that the differential motor DM cannot run until the overskew situation has cleared up.

Mention is here made that if no skew occurs in the moving cloth the excited force transducers 42 give the same voltage outputs; hence, the control system is balanced, ie., there are no unequal electrical output signals transmitted to alter the system balance initially made at the start by the presetting of the potentiometer 7).

It is to be understood, of course, that the various items of electrical apparatus in conjunction with their coacting and related electrical circuits that are illustrated in FIG. 8 usually occupy the interior of the housing of each control amplier unit CA which is indicated in block diagram in the embodiments of the invention shown in FIGS. 1, 4 and 5 of the drawings and therefore should be taken into consideration with each of their particular disclosures and description so that there is no need to augment the description in connection with the above figures with repetitive material which is the same as disclosed in connection with the FIG. 8 circuit diagram.

In FIG. 4 there is shown a modified form of the invention in which the tentering machine of the FIG. l form is disposed in conjunction with and immediately following a tilting roll type straightener S. In this arrangement, however, the differential motor DM has been eliminated and the output voltage from the amplidyne generator AG is fed to the drive motor 8u that operates the straightener rolls 78 and '79.

The manual switches MA and MR are used to control the straightening motor 8f) in cases where it is desired to straighten by hand when the type of cloth does not respond readily to automatic straightening, in which case it is desirable to operate the straightening rolls 78 and 79 tmanually without the automatic.

FIG. shows another modification of the invention in which the FIG. l form of tentering machine is disposed in conjunction with and immediately ahead of a tilting roll type straightener S. In this arrangement the differential motor DM is used together with the drive motor 16 as in the FIG. l arrangement except that in the FIG. 5 showing the control amplifier CA additionally feeds an output voltage to the drive motor Si) of the straightener to operate the rolls 7S and 79 in response thereto to effect skew correction of the woven material leaving the tentering machine.

In accordance with the FIG. 5 arrangement it will be seen that if the entering woven material into the tenter is in a straight condition (without skew) and while being advanced therethrough the selvage edge at one side is ahead and is detected by one of the force-responsive transducers 42 as moving faster than the opposite selvage of the material, then the electrical output signals thusproduced yby the activated transducer 42 are transmitted to the straightener S where they are effective to move its tilting rolls '78 and '79 so as to remove the skew.

A feedback device 82 associated with the straightener S measures the amount of swinging movement of the straightener rolls '7S and 79 and tells the control amplifier l@ CA when these rolls have reached their proper position to remove the detected skew condition, at which time the correcting motor Sil of the straightener stops.

It is to be understood, that, if desired, the FIG. 5 tenter straightener arrangement can be modified along the lines of the FIG. 4 representation using the control system there shown without the differential motor DM but with the straightener S following the tenter as in FIG. 5 and not lahead of said tenter as shown in FIG. 4. Such a tenter assembly is shown in my Patent No. 2,701,405.

While I have illustrated and described several particular embodiments of my invention it will be understood, of course, that such are for the purpose of illustration only, and that I do not wish to be imited thereto since it is feasible that many other modifications and arrangements may be made, and I, therefore, contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of my invention.

What is claimed is:

l. Apparatus for continuously correcting sliew in woven textile material comprising a tenter having drivable members serving to engage the edges of said woven material and advance the said material along the tenter, means for driving said drivable members to operate the same, a variable electro-mechanical drive mechanism operatively connected to said driving means to drive the latter and said drivable members and permit a relative speed variation between the relative speeds of said drivable members, force-responsive means at opposite selvages of said material each operative by applied compressive force applied thereto by coacting portions of said members passing thereby to detect automatically any skew in the traveling Woven material on said tenter and to produce proportional electrical output signals in response thereto, and means operative through said force-responsive detecting means in response to the variations in the electrical output signals derived therefrom for regulating said variable electromechanical drive mechanism to effect a corrective relative speed change of said drivable members through said driving means to eliminate the skew in said woven material as it is delivered from the tenter.

2. Apparatus for continuously correcting skew in traveling woven textile material moving with cloth clips of tenter chains of a tentering machine as the material advances through the latter and in preparation for delivery therefrom comprising means including a drive motor and a differential gearing mechanism operatively arranged for drivin'r said tenter chains, variable control drive means including a differential motor controlled thereby and connected to said differential gearing mechanism effective to operate the chain-driving means to drive both tenter chains and to permit a relative speed variation between the said chains and consequently between the opposite selvage edges of a length of moving woven material held on the chains and traveling therewith through the tentering machine, and force-responsive means for automatically and continuously detecting skew in the moving woven material on said chains, said force-responsive means being actuated both mechanically and electrically by laterally applied pressure exerted thereon by the material engaging portions of the moving chains, the electrical output signals of said force-responsive detecting means derived in consequence of its mechanical actuation being operative through the said differential motor for effecting a corrective relative speed regulation of the tenter chains driven thereby to eliminate the prevailing skew condition of the weft threads in the woven material traveling through the tentering machine.

3. Apparatus for continuously correcting skew in traveling woven textile material moving with cloth clips of tenter chains of a tentering machine while passing through the latter and in preparation for delivery therefrom comprising means including a drive motor and a differential gearing mechanism operatively arranged for driving said tenter chains, variable control drive means including a differential motor controlled thereby and connected to said differential gearing mechanism effective to operate the chain-driving means to drive both tenter chains and,

to permit a relative speed variation between the said chains and consequently between the opposite selvage edges of a length of moving woven material held on the chains and traveling therewith through the tentering machine, and force-responsive means for automatically and continuously detecting skew in the moving woven material on said chains, said force-responsive means being mechanically actuated and including a resistance wire type strain gauge bridge excited electrically in response t laterally applied pressure exerted thereon by the material engaging portions of the moving chains, the electrical output signals of said force-responsive detecting means derived in consequence of its mechanical actuation being operative through the said differential motor for effecting a corrective relative speed regulation of the tenter chains driven thereby to eliminate the prevailing skew condition of the weit threads in the woven material traveling through the tentering machine.

4. Apparatus for continuously correcting skew in traveling woven textile material moving with cloth clips of tenter chains of a tentering machine while passing through the latter and in preparation for delivery therefrom cornprising means including a drive motor and a differential gearing mechanism operatively arranged for driving said tenter chains, an amplidyne control drive system including a control amplifier and a diierential motor controlled thereby and connected to said differential gearing mechanism effective to operate the chain-driving means to drive both tenter chains and to permit a relative speed variation between the said chains and consequently between the opposite selvage edges of a length of moving woven material clampingly held by the chains and traveling therewith longitudinally through the tentering machine, and force-responsive electro-mechanical means for automatically and continuously detecting skew in the moving woven material on said chains, said force-responsive means situated as to be actuated both mechanically and electrically by laterally applied pressure exerted thereagainst by end portions of delivery runs of the moving chains arriving in the vicinity of and entering the operating zone of said force-responsive detecting means, the electrical output signals of said force-responsive detecting means as derived in consequence of its mechanical actuation being fed into the control amplier of said amplidyne control system and effective to produce an output current therefrom for regulating said chain operating ditterential motor to etiect a corrective speed change of the tenter chains and consequently the edges of the clamped woven material moved thereby and accordingly the body of said material traveling in the tenter to eliminate the skew conditions of the weft threads in said woven material.

5. Apparatus for continuously correcting skew in traveling woven textile material moving with cloth clips of tenter chains of a tentering machine while passing through the latter and in preparation for delivery therefrom comprising means including a drive motor and a differential gearing mechanism operatively arranged for driving said tenter chains, an amplidyne control drive system including a control amplifier and a diierential motor controlled thereby and connected to said differential gearing mechanism eliective to operate the chain-driving means to drive both tenter chains and to permit a relative speed variation between the said chains and consequently between the opposite selvage edges of a length of moving woven material clampingly held by the chains and traveling therewith longitudinally through the tentering machine, and force-responsive electro-mechanical means for automatically and continuously detecting skew in the moving woven material on said chains, said force-responsive means including a resistance type strain gauge situated as to be actuated both mechanically and electrically by laterally applied pressure exerted thereagainst by end portions of delivery runs of moving chains arriving inthe vicinity of and entering the operating zone of said force-responsive detecting means, the electrical output signals of said forceresponsive detecting means as derived in consequence of its mechanical actuation being fed into the control amplitier of said amplidyne control system and effective to produce an output current therefrom for regulating said chain operating differential motor to effect a corrective speed change of the tenter chains and consequently the edges of the clamped woven material moved thereby and accordingly the body of said material traveling in the tenter to eliminate the skew conditions of the weft threads in said woven material.

6. Apparatus for continuously correcting skew in woven textile material comprising a tenter having drivable members serving to engage the edges of said woven material and advance the said material along the tenter, longitudinal rail members for guiding said drivable members as they travel, means for driving said drivable members to operate the same, yieldable wall means associated with said rail members, a variable eiectro-mechanical drive mechanism operatively connected to said driving means to drive the latter and said drivable members and permit a relative speed variation between the relative speeds of said members, force-responsive means operative by compressive force applied against said yieldable wall means from coacting portion of said drivable members to detect automatically any skew in the passing woven material on said tenter and to produce proportional electrical output signals in response thereto, and means operative through said force-responsive detecting means in response to the variations in the electrical output signals derived therefrom for regulating said variable electro-mechanical drive mechanism to effect a corrective relative speed change of said drivable members through said driving means to eliminate the skew in said woven material.

7. A method of straightening and correcting skew in a vmoving sheet of woven textile material in a tentering machine comprising the steps of advancing the sheet longitudinally through said machine, electro-mechanically de-4 tecting skew in such advancing tentered sheet material by detecting abnormal deviations from equality of the respective lateral pressure forces present at and imposed by the opposite selvage edges of the moving sheet as a source on the opposite chain drives thereof and producing electrical output signals corresponding to such detected lateral force deviations and proportional to the magnitude of compressive forces transmitted to the chain drives from opposite selvage edges of the moving sheet gripped and advanced thereby as it approaches and reaches its delivery point from the tentering machine, and utilizing the aforementioned electrical output signals to alter and regu' late the relative speeds of feeding movement of the chain drives and the opposite edges of the advancing sheet in the tenter in response to the unequal changes in such electrical output signals occurring by reason of abnormal departures from equality of the lateral compressive forces resulting at the opposite selvage edges of such moving sheet and arising thereat by a skewed condition of the usual transverse weft elements thereof to the usual longitudinal warp elements ofthe sheet and thereby eliminating the latter abnormal skew relationship.

8. Apparatus for straightening and correcting skew in a moving sheet of woven material, comprising drivable means for engaging the edges of said woven material and for advancing the same in a longitudinal direction, force responsive electrical type detecting means located adjacent the edges of said material and responsive to laterally directed compressive forces resulting from the skew condition of said material for detecting the skew condition of said material and for producing proportional output signals in response thereto, means for driving said drivable means and being operative to correct the skew in said material, and means responsive to the electrical output signals from said force responsive detecting means for regulating said driving means, wherein said driving means is effective to correct the skew in said woven material.

9. In combination, drivable means for engaging the edges of a sheet of Woven material and for advancing the same in a longitudinal direction, force responsive electrical resistance type detecting means located adjacent the edges of said material and responsive to laterally directed compressive forces of said material resulting from a skew condition of the weft elements therein for producing proportional electrical output signals, and means responsive to the transmitted electrical output signals from said force 14 responsive detecting means for regulating the longitudinal movement of said drivable means, wherein said drivable means is eiective to straighten the weft elements in said skewed material, thereby correcting the skew condition of said material.

References Cited in the file of this patent UNITED STATES PATENTS 1,754,099 Hamilton Apr. 8, 1930 2,343,328 Robertson et al Mar. 7, 1944 2,701,405 Hoffman Feb. 8, 1955 

9. IN COMBINATION, DRIVABLE MEANS FOR ENGAGING THE EDGES OF A SHEET OF WOVEN MATERIAL AND FOR ADVANCING THE SAME IN A LONGITUDINAL DIRECTION, FORCE RESPONSIVE ELECTRICAL RESISTANCE TYPE DETECTING MEANS LOCATED ADJACENT THE EDGES OF SAID MATERIAL AND RESPONSIVE TO LATERALLY DIRECTED COMPRESSIVE FORCES OF SAID MATERIAL RESULTING FROM A SKEW CONDITION OF THE WEFT ELEMENTS THEREIN FOR PRODUCING PROPORTIONAL ELECTRICAL OUTPUT SIGNALS, AND MEANS RESPONSIVE TO THE TRANSMITTED ELECTRICAL OUTPUT SIGNALS FROM SAID FORCE RESPONSIVE DETECTING MEANS FOR REGULATING THE LONGITUDINAL MOVEMENT OF SAID DRIVABLE MEANS, WHEREIN SAID DRIVABLE MEANS IS EFFECTIVE TO STRAIGHTEN THE WEFT ELEMENTS IN SAID SKEWED MATERIAL, THEREBY CORRECTING THE SKEW CONDITION OF SAID MATERIAL. 